The Global System for Mobile Communications (GSM) is a wireless communication system used for digital cellular telephony. As means having a function of carrying out authentication of a user on the GSM network, and effective accounting management, a Subscriber Identity Module (SIM) is known. As a technique for utilizing the authentication function of the SIM for wireless LAN service, there is an Extensible Authentication Protocol Method for GSM Subscriber Identity Module (EAP-SIM). It should be noted that EAP is a protocol obtained by extending the mechanism of Point-to-Point Protocol (PPP) used in the Internet, and intended for wireless LAN.
Incidentally, in the EAP-SIM, although a protocol is defined between a supplicant corresponding to a data device, and authenticator corresponding to certification authority, this is a protocol corresponding to a configuration having one supplicant and one authenticator.
Accordingly, when a plurality of supplicants are present, although the authenticator needs to execute the aforementioned authentication operation for each of the supplicants, then each of the plurality of supplicants has to carry out an authentication operation together with the authenticator at independent timing, and it is difficult to assure an effective authentication operation due to, for example, signal conflict, repetition of a duplicate operation, and the like.